Ok, what is it that you want to improve on sound wise? I have fairly recently moved from Epos M5 to Monitor Audio RX6. I loved (still do) the Epos, but there was a lack of richness in the mid band that prompted me to upgrade.
Depends too on what sort of budget you've got. I would suggest that to get a night and day upgrade on the M12.2 you might be looking at minimum £800 to £1000 for a pair of standmounts. Although maybe, like I was, you're looking for a different, rather than a better sound?
EDIT: Ah, right, I've just seen the price of those Proacs. I'll leave this one to those with more experience of such hefty price tags!